Dear Adam,
If you go to the "Sixth Marines Home page, on the left are sub-titles, click on each one, there is a "specific on on the "History of the 6th Marines".....also, Barnes and Noble online have "Out of Circulation" Copies of the book "The History of The Sixth Marines"...as well as "The Marshalls" by Lt. Col. Robert Heonze Jr. & Lt. Col. John A. Crown...and "The Recapture of Guam" By Major O.R. Lodge. These will help you descover ALOT about your Grandfathers Division. I also have 2 posts about "Mine", who was with "I" Co. 6th Marine Division, 22nd Marine Regiment, 3rd Battalion, 1st Provisional Marine Brigade that invaded Guam. Although my Grandfather is still with me,(Bless his Heart) and I visit him almost daily to gather info. to write his memoirs.